Combination radio receiver and phonograph



March 22, 1938.-

J. VAN SLQOTEN COMBINATION RADIO RECEIVER AND PHONOGRAPH Filed March 4, 1936 IDDDDDDD .DDDDDD DDIDDPDD blhbhbbb bilhbhbb INVENTOR .J. VAN SLOOTEN BY ATTORNEY Patented Mar. 22, 1938 UNITED STATES COMBINATION RADIO RECEIVER. AND PHONOGRAPH Jacob van- Slooten, Eindhoven, Netherlands, as-

signor to N. V. Philips Gloeilampenfabrieken, Eindhoven, Netherlands Application March 4, 1936; Serial No. 67,004

In Germany March 18, 1935 7 Claims.

This invention relates to a radio receiving set which is adapted at the same time for reproducing talking machine records. With such sets it is known when reproducing records to insert the pick-up in the input circuit of the detector tube which exclusively operates as a low frequency amplifier in this case. After that the amplified voltages are amplified again in a nor mal manner by the further low frequency 19 amplifying part of the set and supplied to the loudspeaker. In many cases, however, this method of changing-over, which is simple and assures sutlicient sound-strength is not feasible, for instance when the detector valve is a diode. In

these cases it would be possible of course, to

interpose the pick-up in the input circuit of the low frequency amplifying part of the sets. It has been found, that in this case the soundstrength is insufficient when reproducing the record, so that it is necessary to interpose either an amplifier or a transformer, which is expensive.

As an alternative the pick-up may be inserted in the input circuit of the last highor intermediate frequency tube which should operate as a low frequency amplifier in this case. When making use of diode rectification the diode detector tube may then be made inoperative during the reproduction of records, since it constitutes a short-circuit for the low frequency currents, and when, as is customary, a tuned circuit is inserted in the output. circuit of the tube, this tuned circuit should be replaced by a coupling resistance. Moreover, the coupling condenser should be enlarged. It will be obvious that the changing-over arrangement becomes fairly complicated in this way.

The object of the present invention is to provide a circuit arrangement in which one of the highor intermediate frequency tubes is adapted in a simple manner for low frequency amplification when reproducing records.

According to the invention the screen grid of the said tube is used as an anode when records are reproduced. For this purpose a coupling resistance is inserted in the screen-grid circuit, the screen-grid being connected to the input circuit of the low frequency amplifying part of the set through a coupling condenser. It has been 50 found that in this manner a sufficient preliminary amplification of the low frequency currents can be achieved.

The invention will be more clearly understood by reference to the accompanying drawing representing by way of example, that part of the set according to the invention which is relevant to the latter.

When receiving radio signals the high or intermediate frequency oscillations are supplied between the grid 18 and the cathode 19 of a screened-grid tube I. Through the switch I, which bears on the left contact during radio reception, the screen-grid I1 is connected to a point of positive voltage, for instance to the positive terminal of the supply, so that the resistance 5 is short-circuited. The anode is connected to the positive pole of the supply through a tuned circuit It. The amplified voltages are supplied to the detector circuit through a coupling condenser 9. The detector circuit comprises a diode 2, a resistance 1 l, whose function will be set out hereinafter, and a potentiometer resistance 12, from which low frequency voltages are taken off through a contact I3 by the adjustment of which the sound strength can be controlled. The resistance H may be connected in series with a high frequency choking coil 20. The condenser I0 is designed for carrying off the highor intermediate frequency voltages. The low frequency voltages are supplied to the output Valve 3 in whose output circuit a transformer 14 may be inserted, whose secondary winding is connected to the loudspeaker 15.

When changing over from the reception of radio signals to record-reproduction by changing over the switch 6, the pick-up 4 is inserted in the input circuit of the tube 1. At the same time the commutator i is changed over thus contacting with the right contact, the resistance 5 being inserted in the screen-grid circuit. In this case the tube I operates as a low frequency amplifier, the screen-grid ll serving as an anode. The low frequency voltages are supplied to the resistance 12 through the coupling condenser 8. The resistance ll prevents the low frequency voltages from flow off through the diode.

I claim:

1. In amplifying apparatus, an amplifier inquency output circuit between the auxiliary electrode and the cathode of the tube.

2. In amplifying apparatus, an amplifier including an electronic tube having an anode, a cathode, a control grid and an auxiliary electrode, a high frequency input circuit for said tube connected between the control grid and the cathode, a high frequency output circuit for said tube connected between the anode and the oathode, a detector connected in the output circuit of said electronic tube, and an audio frequency amplifier connected to the detector, a low frequency circuit and switching means for connecting the low frequency circuit between the control grid and cathode of the first tube, and means including a switching device for connecting the auxiliary electrode of the first named tube to the audio frequency amplifier.

3. In a radio phonograph system, a high frequency amplifier including a space discharge device having an anode, a cathode, a control grid and auxiliary electrode, a diode detector connected between the anode and cathode of said space discharge device, an audio frequency amplifier connected to the diode output, a phonograph pick-up means and means including a switch for connecting the phonograph pick-up means between the control grid and cathode of the first named tube, and switching means for changing the characteristics of the first named tube so that the auxiliary electrode acts as an anode with respect to the control grid and cathode, and to connect the auxiliary electrode to the audio frequency amplifier when the first named tube is adjusted to act as an amplifier for phonograph signals.

4. In a radio phonograph device, an amplifier including a space discharge device provided with an anode, a cathode, a signal grid and an auxiliary electrode, a high frequency input circuit connected between the signal grid and the oathode, a low frequency input circuit including the phonograph pick-up device and a switching means for connecting said low frequency input circuit between the signal grid and the cathode of said first tube, a diode rectifier, means including a coupling condenser for connecting the anode of the first tube to the anode of the rectifier, a connection between the anode and cathode of the rectifier including an inductance coil and a pair of resistors in series, means including a resistance element for connecting the auxiliary electrode of the first named tube to a positive source of current, and means including a tuned circuit for connecting the anode of the first tube to the positive terminal of the source of current, means comprising an operable switching device and a coupling condenser in series, adapted to connect the auxiliary electrode of the first tube to a point intermediate said two resistors, said switching device also being adapted to short-circuit the resistance connected between the auxiliary electrode and the positive terminal of the source of space current, an audio frequency amplifier including a control electrode, a cathode and an anode, and means including a condenser for connecting the control electrode to a point of that one of said two mentioned resistors between the anode and cathode of the diode which is nearest the cathode.

5. In amplifying apparatus, a high frequency amplifier circuit including an electronic tube having an anode, a cathode, a signal grid and an auxiliary electrode, external circuits for said tube forming a signal grid-cathode circuit, an auxiliary electrode-cathode circuit and an anode-cathode circuit, a low frequency amplifier provided with an input circuit and an output circuit, a detector interposed between the anode-cathode circuit of said electronic tube and the input of the low frequency amplifier, a low frequency circuit including a photograph pickup device, switching means for connecting the low frequency circuit to the signal grid-cathode circuit of said electronic tube, and switching means for connecting said auxiliary electrode-cathode circuit of said electronic tube directly to the input of said low frequency amplifier when the low frequency circuit is switched into the signal gridcathode circuit of said electronic tube.

6. An arrangement as described in claim 5 characterized by that the auxiliary electrode operates as an anode when the last named switching means is operated to connect the high frequency amplifier and the low frequency amplifier directly.

'7. In a radio phonograph combination, a high frequency amplifier circuit, a detector circuit and a low frequency amplifier circuit coupled in cascade in the order named, said high frequency amplifier including an electronic tube having an anode, a cathode, a signal grid and an auxiliary electrode, a circuit including a phonograph pickup device, means for connecting said circuit in the input of the high frequency amplifier, an auxiliary output circuit for said high frequency amplifier comprising means connected between the auxiliary electrode and the cathode, said means including a switching device, and. means connecting said last named circuit to the input of the low frequency amplifier, said detector circuit including means for preventing energy transferred from the phonograph pick-up device through the first amplifier circuit from traversing the detector circuit when the last named switching means is operated so as to connect the first named amplifier to the low frequency amplifier through the auxiliary output circuit.

JACOB VAN SLOOTEN. 

